CHAPTER VI. THE JOINTS.
Temporo-Mandibular Joint.—This joint has the same general structure as in Han, but the mandible moves in a shallower elenoid cavity. The capsule is
C3 t. 4.
thick and strong except on its anterior and inner aspects. Its cavity is divided into upper and lower parts by the meniscus, which is concavo-convex above and concave below. The disc, which is thicker in front, is attached in some Apes to the glenoid and post-glenoid processes. It is not perforated in the Orang and Chimpanzee. The external lateral ligament is strong in all Apes, The posterior temporo-inandibular, internal temporo-man-dibular and stylo-mandibular ligaments are well defined, but the spheno-mandibular band is poor. The external pterygoid muscle is partly inserted into the capsule.
Vertebral Ligaments.—The anterior and posterior common ligaments run from the axis to the upper segment of the sacrum. The former is attached to the centra, but not to the intervertebral discs; and the latter is narrow on the centra and expanded on the discs. The supraspinous and interspinous ligaments are as in Man but the ligamentum nuchse is absent or represented merely by a little fibrous tissue between the muscles. The ligamenta subflava are very elastic, as are the posterior costo-transverse ligaments. The inter-